It was very slight—not more than an eighth of an inch in width—and would never be detected by a person while standing erect. He would have to stoop to find it. Was there any meaning to this? Could the ponderous block possibly be tilted over toward that easterly end?
Just half its bulk at bottom appeared to be free from resting upon the floor beneath, so there might be just that eighth of an inch play in case it could be moved.
Percy looked the ground over once more, and then went around to the opposite—the westerly—end of the altar. That was where the spectral monk had last been seen.
Could the massive block be jostled? He laid his hands upon the upper edge, then stooped slightly, so as to lift at the stone when he should put forth his strength, and then made the trial. He did not apply his full force in the outset. It was an experiment, and he wished to note particularly the result.
With his two hands fixed in place, and his lower limbs firmly braced, he lifted, lightly at first, and then with renewed force.
By and by, acting upon the impulse of the moment, he gave a sudden upward pressure with all his might. The result was wonderful.
First, he felt the heavy mass yield; next, he heard a dull thud followed by a rattling, grating sound beneath the floor; and, a moment later, the ponderous cube, starting away from its rest against the rear wall of the chapel, swung outward for a distance equal to its own depth, perhaps a little more.
And there, exposed to his view, was an opening in the pavement seemingly as long and as broad as the altar would safely cover; and on looking down he saw the head of a ladder resting against the side nearest to him.
His first thought was of the mechanism by which this wonderful result had been wrought; and for the purpose of discovering that he went part way down the ladder. He examined thoroughly, and found it very nearly as he had thought. A system of enormous weights, slung in chains of copper, the chains working in easily running blocks, were so arranged that upon setting the weights free the stone would be moved, as we have seen. The huge stone itself swung upon a pivot, at the inner, eastern corner, and at the other end underneath were small trucks on which it traveled over the flagging, and which had caused the abrasions which had attracted the explorer’s attention.
The tipping of the rock backward set the spring free, and our hero remembered that he had instinctively applied his force towards moving the stone away from the wall until it had stopped, and then he had heard a sharp click, as though another spring had been caught.